webpack.config.js

// base config file, rails and hotloader will manage the rest
var path = require("path");
var webpack = require("webpack");

module.exports = {
  entry: {
    app: [
      'webpack-dev-server/client?http://localhost:8080/assets/',
      'webpack/hot/only-dev-server',
      './scripts/init.js.jsx'
    ]},
  ouput: {
    path: "../app/assets/javascripts",
    publicPath: 'http://localhost:8080/javascripts/',
    filename: "bundle.js"
  },
  resolve: {
    extensions: ["", ".webpack.js", ".web.js", ".js", ".jsx", ".config.js"]
  },
  devtool: "#eval-source-map",
  module: {
    loaders: [
      { test: /\.jsx$/, loaders: ["react-hot", "babel", "jsx-loader"], exclude: /node_modules/  },
      { test: require.resolve("jquery"), loader: "expose?jQuery" },
      { test: require.resolve("jquery"), loader: "expose?$" },
    ]
  }
};

webpack.production.js

var config = require("./webpack.config");

config.entry = {
  app: [
    "./scripts/init.js.jsx"
  ]
};

config.output = {
  filename: "bundle.js",
  path: "../app/assets/javascripts"
};

config.devtool = {};

module.exports = config;